1. Field of the Invention
The present invention relates to a process for regenerating a catalyst of the type used in hydrocarbon conversion processes. More particularly, this invention relates to a process for regenerating a catalyst comprising fluorosulfuric acid, said catalyst having become at least partially deactivated due to the formation of dilvents during contact with a hydrocarbon feedstock in an alkylation process.
2. Description of the Prior Art
It is well known in the prior art that as the alkylation reaction proceeds, an organic material will form and will accumulate in the fluorosulfuric acid catalyst phase. The material has been given a variety of names including red oil, sludge, organic sludge, acid-oil and the like. This organic material is a natural by-product of acid-catalyzed hydrocarbon reactions such as occur during alkylation and has been described in the literature as a conjunct polymer (see Miron, S. and Lee, R.J., "Molecular Structure of Conjugated Polymers", J. Chem. Eng. Data, Vol. 8, pp. 150-160 1963), the disclosures of which are incorporated herein by reference. These conjunct polymers are complex mixtures of olefinic, conjugated cyclic hydrocarbons that may be formed from any type of hydrocarbon except aromatics. More specifically, they are believed to be cyclic polyolefinic hydrocarbons with a high proportion of conjugated double bonds, no two of which are in the same ring. Five membered ring systems predominate, but larger, and possibly also smaller, rings are believed to be present. The accumulation of this material will ultimately cause the activity of fluorosulfuric acid catalysts to decline until said catalysts cease to exhibit economic activity. In such cases, depending upon economic factors, the catalyst may be replaced or regenerated to restore desired activity levels.
One method for regenerating catalysts comprising fluorosulfuric acid has been suggested in U.S. Pat. No. 3,766,293, the disclosures of which are incorporated herein by reference. According to this method, an alkylation catalyst comprising fluorosulfuric acid, at least a portion of which has become deactivated, may be regenerated by (1) contacting said catalyst with water so as to convert at least a portion of the fluorosulfuric acid to hydrogen fluoride and sulfuric acid; (2) removing at least a portion of the hydrogen fluoride from said catalyst by contacting the same with a paraffin so as to form a hydrocarbon phase containing hydrogen fluoride; and (3) treating said hydrocarbon phase with sulfur trioxide to regenerate the fluorosulfuric acid. In application Ser. No. 772,637 filed on the same date herewith, there is disclosed a method for regenerating fluorosulfuric acid catalysts which employs refrigeration and cooling of the hydrocarbon phase to provide a stripping gas of low fluoride content. While the above methods are effective in regenerating said catalyst, it is believed that the particular regeneration technique described hereinbelow has certain advantages over those disclosed in U.S. Pat. No. 3,766,293 and application Ser. No. 772,637, which heretofore have not been disclosed.